LIQUID CRYSTAL DISPLAY DEVICE AND DRIVING METHOD THEREOF

• US 20110032283A1
• Filed: 08/03/2010
• Published: 02/10/2011
• Est. Priority Date: 08/04/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Baek, Heume Il
• Granted Patent: US 8,648,886 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 2370/08 Details of image data interface between the display device controller and the data line driver circuit
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

An LCD device and a driving method thereof are discussed. The LCD device can prevent a blended color within each block which is defined in an LCD panel. To this end, the LCD device divides an external image data into a plurality of block image data, generates first dimming signals opposite to red, green, and blue data with each block image data, and provides a second dimming signal opposite to a brightness data with each block image data. Also, the LCD device calculates a difference value between maximum and minimum grayscale values by analyzing histograms for the red, green, and compares the calculated difference value with a reference difference value. Furthermore, the LCD device allows one of the first and second dimming signals to be selected according to the dimming mode control signal.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display panel configured to include a plurality of liquid crystal cell formed on regions which are defined by a plurality of gate lines and a plurality of data lines;

a backlight unit configured to irradiate light on the liquid crystal display panel using a plurality of light emission diode arrays each with a plurality of light emission diodes;

a first dimming signal generator configured to divide an external image data into a plurality of block image data and to generate first dimming signals opposite to red, green, and blue data with each block image data;

a second dimming signal generator configured to generate a second dimming signal opposite to a brightness data with each block image data;

a dimming mode controller configured to calculate a difference value between maximum and minimum grayscale values by analyzing histograms for the red, green, and blue data with each block data, to derive a dimming mode control signal from the difference value;

a selector configured to select one of the first and second dimming signals in accordance with the dimming mode control signal from the dimming mode controller; and

a light emission diode driver configured to drive the plurality of light emission diodes with each of the plural light emission diode arrays which are opposite a plural blocks.

2. The liquid crystal display device claimed as claim 1, wherein the dimming mode controller includes:

a histogram analyzer configured to analyze the block histograms for the red, green, and blue data with each block image data;

a maximum grayscale difference calculator configured to derive the difference value between the maximum and minimum grayscale values from the block histograms provided by the block histogram analyzer;

a gain calculator configured to derive a gain value from the grayscale difference value; and

a comparator configured to generate the dimming mode control signal with one of different logic levels by comparing the calculated gain value with a reference gain.

3. The liquid crystal display device claimed as claim 2, wherein the block histogram analyzer is further configured to provide at block accumulation histogram for the red, green, and blue pixel data within each block image data;

and the gain calculator is further configured to set the gain value at a maximum value when the difference value is a reference difference value or less, and to derive the gain value from the block accumulation histogram provided by the block histogram analyzer.

4. The liquid crystal display device claimed as claim 3, wherein the gain calculator is configured to obtain the gain value from the below equation 1.

5. The liquid crystal display device claimed as claim 2, wherein the reference gain value corresponds to a proportion of pure chromatic color components with respect to the total color components within the block image data when the pure chromatic components of high chroma levels with non-chromatic color components is included in the block image data, and has a range of 1˜

2.

6. The liquid crystal display device claimed as claim 1, wherein the first dimming signal generator is configured to calculate mean values for the red, green, and blue pixel data with each block image data and to derive the first dimming signals from the red, green, and blue mean values.

7. The liquid crystal display device claimed as claim 5, wherein the second dimming signal generator is configured to select the highest mean value from the red, green, and blue mean values generated in the first dimming signal generator, and to derive the second dimming signal from the selected highest mean value.

8. The liquid crystal display device claimed as claim 1, wherein the dimming mode controller includes:

a histogram analyzer configured to analyze the block histograms for the red, green, and blue data with each block image data;

a maximum grayscale difference calculator configured to derive the difference value between the maximum and minimum grayscale values from the block histograms provided by the block histogram analyzer; and

a gain calculator configured to derive a gain value from the grayscale difference value; and

a comparator configured to generate the dimming mode control signal with one of different logic levels by comparing the calculated difference value with a reference gain, and to apply the dimming mode control signal to the selector.

9. A method of driving a liquid crystal display device including:

a liquid crystal display panel configured to include a plurality of liquid crystal cell formed on regions which are defined by a plurality of gate lines and a plurality of data lines; and

a backlight unit configured to irradiate light on the liquid crystal display panel using a plurality of light emission diode arrays each with a plurality of light emission diodes, the method comprising;

dividing an external image data into a plurality of block image data and generating first dimming signals opposite to red, green, and blue data with each block image data;

generating a second dimming signal opposite to a brightness data with each block image data;

calculating a difference value between maximum and minimum grayscale values by analyzing histograms for the red, green, and blue data with each block data, deriving a gain value from the difference value, and generating a dimming mode control signal with one of different logic levels by comparing the gain value with a reference gain value;

selecting one of the first and second dimming signals according to the dimming mode control signal; and

generating driving voltages necessary to drive the plurality of light emission diodes with each of the plural light emission diode arrays, which are opposite a plural blocks, according to the selected dimming signal.

10. A method of driving a liquid crystal display device including:

a liquid crystal display panel configured to include a plurality of liquid crystal cell formed on regions which are defined by a plurality of gate lines and a plurality of data lines; and

a backlight unit configured to irradiate light on the liquid crystal display panel using a plurality of light emission diode arrays each with a plurality of light emission diodes, the method comprising;

dividing an external image data into a plurality of block image data and generating first dimming signals opposite to red, green, and blue data with each block image data;

generating a second dimming signal opposite to a brightness data with each block image data;

calculating a difference value between maximum and minimum grayscale values by analyzing histograms for the red, green, and generating a dimming mode control signal with one of different logic levels by comparing the gain value with a reference difference value;

selecting one of the first and second dimming signals according to the dimming mode control signal; and

generating driving voltages necessary to drive the plurality of light emission diodes with each of the plural light emission diode arrays, which are opposite a plural blocks, according to the selected dimming signal.